Strip Guide for High-Speed Continuous Application of a Strip Material to a Moving Sheet-Like Substrate Material at Laterally Shifting Locations

ABSTRACT

Disclosed are examples of a strip guide for laterally shifting a longitudinally moving strip material as it enters a joining mechanism that urges the strip material into contact with a moving sheet material, the strip guide comprising a surface over which the strip material passes longitudinally, the surface defining a U-shape.

FIELD OF THE INVENTION

This invention relates to a system, components thereof, and method forcontinuously applying and affixing a strip material to a sheet-likesubstrate material moving longitudinally through a manufacturing line,at laterally shifting locations on the substrate material. Moreparticularly, the present invention relates to a system and componentsthat continuously draw respective strip material and sheet-likesubstrate material from continuous supplies, and laterally shift thestrip material across the machine direction of the substrate material asthe two materials enter a joining mechanism that affixes the stripmaterial onto the substrate material. The invention also relates to asystem, components thereof, and method for continuously regulating thestrain in a longitudinal material as it enters a joining mechanism.

BACKGROUND OF THE INVENTION

Currently, wearable articles such as disposable diapers, disposabletraining pants, disposable adult incontinence garments and the like areconstructed of various types of sheet- or strip-like materials. Thesematerials may include nonwoven webs formed of synthetic polymer and/ornatural fibers (“nonwovens”), polymeric films, elastic strands, stripsor sheets, or assemblies or laminates of these materials. In a typicalarticle, nonwovens and/or laminates of various types form at least onecomponent of an outer garment-facing layer (“backsheet”), an innerbody-facing layer (“topsheet”) and various internal layers, cuffs,envelopes or other features, depending upon the particular features ofthe product. The component sheet- or strip-like materials are usuallysupplied in the form of large continuous rolls, or alternatively, boxesof continuous longitudinal sheet or strip material gathered and foldedtransversely in accordion fashion.

The articles are typically manufactured on relatively complexmanufacturing lines. Supplies of the required materials are placed atthe front of each line. As a line requires the materials for themanufacture of articles, it continuously draws the materialslongitudinally from their respective supplies. As a particular materialis drawn from the supply and proceeds through the line to beincorporated into final product, it may be flipped, shifted, folded,laminated, welded, stamped, embossed, bonded to other components, cut,etc., ultimately being fashioned by the machinery into an incorporatedpart of the finished product. All of this happens at theeconomically-required production rate, e.g., 450 or more product itemsper line per minute. Generally, for purposes of economy, increasing theproduction rate is an ever-present objective.

A new design for a wearable absorbent article such as a disposablediaper, training pant or adult incontinence undergarment has beendeveloped. The article has features that give it an underwear-brief-likefit, feel and appearance, which consumers may find appealing. Among thefeatures that give it this fit, feel and appearance are elastic bandsabout respective leg openings that encircle the wearer's legs. Theelastic bands may be formed of, for example, one or more strands orstrips of an elastic material such as spandex, bonded with one or morestrips of nonwoven or film material to form a band-like elastic stripmaterial. On the subject wearable absorbent article design, theseelastic bands are affixed or bonded to the outer surface of a substrateouter cover (backsheet) material, with the lower side edges of each ofthe elastic bands being substantially coterminous with each of therespective leg openings to create a neatly finished, banded appearance.The elastic strip material may be longitudinally strained prior toaffixation to the backsheet material, whereby subsequent relaxation ofthe elastic strip material causes the backsheet material to gather aboutthe leg openings, for improved fit and comfort.

To date, the subject design has been produced only by hand manufacturingor limited machine-assisted manufacturing techniques, at rates that aretoo low for economically feasible production of the design as a viable(i.e., competitively priced) consumer product.

Among the problems that the design presents is determining how theelastic strip material can be accurately placed and affixed to thesubstrate backsheet material at locations required by the design and ateconomically feasible production speeds, e.g., 450 items or more perminute, in a manner that is reliable, minimizes waste, and maximizesconsistency and quality of the band placement and affixing process. Itis envisioned that strip material will be applied and affixed tosubstrate backsheet material at laterally varying design-requiredlocations, as the substrate material moves longitudinally through themanufacturing line at production speed. Under these circumstances, oneparticular problem lies in determining how to rapidly and repeatedlylaterally shift back and forth the point at which such strip materialenters a joining/bonding mechanism, without causing the typicallypliable, cloth-like strip material to “rope” (longitudinally fold orbunch over on itself) before it enters the joining/bonding mechanism.

A potential associated problem lies in regulating the strain of theelastic strip material as it is affixed to a substrate material. Ifelastic strip material under longitudinal strain is shifted laterallybetween two points at which it is gripped, this will cause variation inthe strain. Thus, shifting elastic strip material laterally as it isbeing affixed to substrate material may result in variation in thelongitudinal strain of the strip material as affixed to the substrate.In some circumstances this may have undesirable effects.

It would be advantageous if a system, apparatus and method existed toaddress the problems referenced above.

SUMMARY OF THE INVENTION

In one example, the invention may include a strip guide for laterallyshifting a longitudinally moving strip material as it enters a joiningmechanism that urges the strip material into contact with a moving sheetmaterial, the strip guide comprising a surface over which the stripmaterial passes longitudinally, the surface defining a U-shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective sketch of a wearable article as it may be wornby a person;

FIG. 2 is a plan view of an outer chassis component of a wearablearticle such as that shown in FIG. 1, shown laid flat, outside(garment-facing) surface facing the viewer, prior to completion of thewearable article;

FIG. 3 is a plan view of a partially completed portion of material fromwhich an outer chassis component such as that shown in FIG. 2 may becut;

FIG. 4 is a perspective view of components of a system including a pairof strip guide arms and a joining mechanism;

FIG. 5 is a schematic view of a pair of strip guide arms shown guidingstrip material into a pair of joining rollers;

FIGS. 6A-6D are perspective, side, front and rear views, respectively,of a strip guide arm;

FIG. 7 is a perspective view of another embodiment of a strip guide arm;

FIG. 8 is a schematic side view of a system including a feed mechanism,strip guide arm, servo motor, and joining mechanism, shown in theprocess of affixing a strip material to a sheet material;

FIG. 9 is a schematic top view of a system including a feed mechanism,strip guide arm, servo motor, and joining mechanism, shown in theprocess of affixing a strip material to a sheet material;

FIG. 10 is a schematic side view of a system including a feed mechanism,another embodiment of a strip guide arm, servo motor, and joiningmechanism, shown in the process of affixing a strip material to a sheetmaterial;

FIGS. 11 a and 11 b are perspective views of a strip guide arm in twodiffering positions, respectively, shown with strip material lyingtherealong;

FIGS. 11 c and 11 d are perspective views of a system including a stripguide arm in two differing positions, respectively, shown with stripmaterial lying therealong and moving therethrough, and downstream towarda pair of joining rollers; and

FIG. 12 is a schematic side view of a system including a feed mechanism,strip guide arm, servo motor, and joining mechanism, shown in theprocess of affixing a strip material to a sheet material;

FIG. 13 is a schematic top view of a system including a feed mechanism,strip guide arm, servo motor, and joining mechanism, shown in theprocess of affixing a strip material to a sheet material;

FIG. 14 is a geometric schematic diagram illustrating examples of strippath lengths varying as a result of pivoting of a strip guide arm;

FIG. 15A is a schematic plan view of respective portions of a substratematerial and an elastic strip material, shown unruffled and relaxed,respectively;

FIG. 15B is a schematic plan view of respective portions of a substratematerial shown unruffled and an elastic strip material shown in astrained condition;

FIG. 15C is a schematic plan view of a portion of a substrate materialshown with rugosities along an affixed portion of an elastic stripmaterial in a relaxed condition; and

FIG. 15D is a schematic plan view of a portion of a substrate materialshown with rugosities along an affixed portion of an elastic stripmaterial in a relaxed condition.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

DEFINITIONS

For purposes of this description, the following terms have the meaningsset forth below:

Connected: With respect to a relationship between two mechanicalcomponents, unless otherwise specified, “connected” means that thecomponents are directly physically connected to each other, orindirectly physically connected to each other through intermediatecomponents. Unless otherwise specified, “connected” is not meant toimply or be limited to a connection that causes the components to becomeimmovably fixed with respect to each other.

Continuous supply: With respect to a supply of sheet- or strip-likematerials forming components of a product, means a length of suchmaterial on a roll, or folded accordion-fashion (“festooned”), wherebythe material may be drawn therefrom in longitudinal or linear fashion bymachinery, to manufacture a quantity of items or products from one suchlength. Noting that such lengths are not of infinite length, “continuoussupply” is not intended to exclude, but also is not intended tonecessarily mean, a supply that is infinite or without end.

Downstream: With respect to components of a manufacturing line, relatesto the direction or orientation of forward travel of materials throughthe manufacturing line toward completion of a product.

Lateral (and forms thereof): With respect to the machine direction,means transverse to the machine direction.

Longitudinal (and forms thereof): With respect to a feature of amechanical system component or component of a product, meanssubstantially parallel to or along the line of the longest dimension ofthe component.

Machine direction: With respect to a component of a product, refers toany line along the component substantially parallel to the direction offorward travel of the component through the manufacturing line towardcompletion of a product.

Servo motor: Any rotary electric motor having a rotating output driveshaft, which motor is adapted to be controlled such that the drive shaftcan be caused to rotate (within performance limits) at constant, varyingand continuously varying, user-selected or user-programmed: angularvelocity, angular acceleration/deceleration, rotational direction and/orrotational stop or reversal position.

Strip material: Means any band-like, strip-like, strap-like, orribbon-like material that, when longitudinally extended, has a greatestlongitudinal dimension, and a cross section in a plane substantiallyperpendicular to the longitudinal dimension, the cross section having anaspect ratio, or a ratio of width to thickness, equal to or greater thanabout 2.5. The term includes but is not limited to materials that havesubstantially rectangular or substantially oval cross sections, as wellas elongated but irregular cross sections. The term includes but is notlimited to materials that are natural or synthetic, cloth or cloth-like,woven or nonwoven, or film, and includes but is not limited to materialsthat are inelastic, elastic and/or elasticized. The term includes but isnot limited to homogeneous strip-like materials, fibrous strip-likematerials and assembled or composite strip-like materials, such aslaminates or other assemblies of differing materials such as an assemblyof one or more elastic strands or strips situated next to one, orbetween two or more, strips of film, cloth or nonwoven material.

Upstream: With respect to components of a manufacturing line, relates tothe direction or orientation opposite that of forward travel ofmaterials through the manufacturing line toward completion of a product.

Example of Wearable Article and Manufacturing Problems Presented

An example of a product such as wearable article 10 as it may be worn bya person is depicted in FIG. 1. The wearable article 10 has agarment-facing outer cover or backsheet 20, a waistband 30 and a pair oflegbands 40. The backsheet 20 may be elastic or stretchable, and may beformed at least in part of a nonwoven or laminate of a nonwoven and apolymeric film. Various possible examples of backsheet materials aredescribed in U.S. Pat. Nos. 6,884,494; 6,878,647; 6,964,720; 7,037,569;7,087,287; 7,211,531; 7,223,818; 7,270,861; 7,307,031; and 7,410,683;and in U.S. Published Applications, Publication Nos. 2006/0035055;2007/0167929; 2007/0218425; 2007/0249254; 2007/0287348; 2007/0293111;and 2008/0045917.

In order that they may contribute to the desired fit, feel andappearance, it may be desirable to form waistband 30 and legbands 40 atleast partly of an elastic material such as an elastic strip material.The elastic strip material may be formed, for example, by sandwichingone or more strands or strips of elastic polymer material between, forexample, two outer strips of nonwoven and/or film. In one example, theelastic strip material may be formed by first longitudinally stretchingthe one or more strands or strips of elastic polymer material, and thenbonding the two outer strips of nonwoven and/or film on either sidethereof to sandwich the stretched elastic polymer material therebetween.When the elastic polymer material is allowed to relax it will cause thebonded strips of nonwoven and/or film to ruffle transversely. Theresulting transverse rugosities will comprise longitudinally gatheredmaterial which accommodates longitudinal stretching along with theelastic strip material. In a particular example, an elastic stripmaterial may be formed of a plurality, for example, three to nine,strands of elastomeric material such as spandex, sandwiched between twoouter strips of nonwoven and/or film bonded together, wherein theelastomeric strands are stretched prior to bonding, resulting in anelastic strip material having transverse rugosities of outer material.In another example, an elastic strip material may be formed of a stripof elastic film, or one or more elastic strands, bonded to a singlestrip of nonwoven or film, on one side only. In another example, anelastic strip material may be formed of a single strip of elastic filmmaterial, or single strip of nonwoven material having desired inherentelastic properties.

For purposes of balancing objectives of economy, appearance, fit andcomfort, the strip material for the waistband 30 may be, for example,approximately 10-50 mm wide, or approximately 10-35 mm wide, orapproximately 10-30 mm wide, or even approximately 10-25 mm wide. Usingtypical materials, the strip material for the waistband may be, forexample, approximately 1-4 mm thick, or even approximately 1.5-2.5 mmthick, in the relaxed and uncompressed state. Thus, the particular stripmaterial used for the waistband may have a cross-section substantiallyperpendicular to its longest longitudinal dimension, the cross sectionhaving an aspect ratio within a broad range of approximately 10:4 (2.5)to 50:1 (50), within a narrow range of approximately 10:4 (2.5) to 25:1(25), or within any intermediate ranges calculated from the width andthickness ranges set forth above.

For purposes of balancing objectives of economy, appearance, fit andcomfort, the strip material for the legbands 40 may be, for example,approximately 10-30 mm wide, or approximately 10-25 mm wide, orapproximately 10-20 mm wide, or even approximately 15-20 mm wide. Usingtypical materials, the strip material for the legbands may be, forexample, approximately 1-4 mm thick, or even approximately 1.5-2.5 mmthick, in the relaxed and uncompressed state. Thus, the particular stripmaterial used for the legbands may have a cross-section perpendicular toits longest longitudinal dimension, the cross section having an aspectratio within a broad range of approximately 10:4 (2.5) to 30:1 (30),within a narrow range of approximately 15:4 (3.75) to 20:1 (20), orwithin any intermediate ranges calculated from the width and thicknessranges set forth above.

In one example, an elastic strip material of which elastic legbands 40and/or waistband 30 may be formed may be longitudinally strained priorto being affixed to backsheet 20, and affixed to backsheet 20 while inthe strained state. Following affixation to backsheet 20 and completionof the article, relaxation of waistband 30 and/or legbands 40 will causethe waist and/or leg openings in the article to gather so as to fit moresnugly and comfortably about the waist and legs of a wearer.

FIG. 2 is a plan view of the garment-facing side of outer chassis 28 ofa wearable article such as depicted in FIG. 1, laid flat, prior to finalassembly, with affixed elastic strip material. Outer chassis 28 includesbacksheet 20 with affixed elastic front and rear waistband portions 30a, 30 b and legbands 40. To form completed article 10 (FIG. 1), outerchassis 28 (FIG. 2) may be folded laterally at or about lateral line 35,garment-facing side out, to bring front waist edges 24 into overlappingcontact with rear waist edges 26. The respective overlapping waist edgepairs may then be affixed together in any suitable manner, such as bycompression bonding, adhesive bonding, ultrasonic bonding, etc., to formside seams 25 (FIG. 1).

Outer chassis 28 may be formed by cutting the design profile of theouter chassis from a continuous sheet of material having elastic stripmaterial already affixed thereto, in the required locations, in upstreamprocesses. FIG. 3 depicts a plan view of a partially completed portion51 of an outer chassis, formed from a continuous supply of substratebacksheet material 50, with continuous lengths of strip material 42affixed thereto, as the portion may appear in the manufacturing linefollowing affixation of the strip material 42 to the backsheet material50. Following affixation of strip material 42 to backsheet material 50in the configuration shown in FIG. 3 (and, possibly, application ofadditional elastic strip material (not shown) to form a waistband),partially completed portion 51 may be cut along backsheet design profile21 (indicated by dashed line in FIG. 3) to create an outer chassis 28(FIG. 2).

The present invention might be deemed useful for any purpose thatincludes applying a strip material to a substrate material in laterallyvarying locations on the substrate material. Thus, in one example, thepresent invention may be deemed useful in connection with the location,application and affixation of a strip material to a substrate materialto form a product or a portion thereof, such as, for example, partiallycompleted portion 51 (FIG. 3) of an outer chassis of a disposablewearable article. The present invention may be deemed particularlyuseful for this purpose at production speeds exemplified by a disposablewearable article manufacturing line. A typical manufacturing line of thekind used to manufacture wearable articles of the kind described mayproduce 450 or more finished product items per minute. At 450 items perminute, backsheet material 50 may move longitudinally through the lineat approximately 206 meters per minute in a machine direction asindicated by the arrow in FIG. 3. Referring to FIG. 3, equipment isrequired that laterally shifts strip material 42 for affixing to asubstrate at required locations on a repeating basis at thecorresponding rate, e.g., of 450 cycles per minute (7.5 cycles persecond) or more. The equipment should be able to substantiallyaccurately locate strip material 42 in laterally varying locations suchas shown in FIG. 3, and then affix the strip material 42 to thebacksheet material 50 in those locations. Also, as previously mentioned,it may be desired to longitudinally strain strip material 42 prior toaffixation to backsheet material 50, and to be able to locate and affixthe strip to the backsheet material in the strained condition.

For purposes such as those described herein it may be desirable thatstrip material 42 be applied and affixed to substrate backsheet material50 in a flat condition, which helps provide a leg band that is ofuniform width (e.g., the width of the strip) and thickness, and liesflat on the substrate material. It also may be desirable that stripmaterial 42 be applied by a method that minimizes a decrease in appliedstrip width that may result in “contour error”. Unacceptable contourerror may result from laterally shifting a strip material, as it isbeing drawn through a nip point between rollers, so abruptly that thenip point does not have sufficient time to shift with the lateralmovement, such that the strip is drawn askew.

Under certain manufacturing conditions, a pliable strip material may,even under longitudinal tension, exhibit a tendency to longitudinallyfold or bunch over onto itself, or “rope,” as machine components shiftit laterally at required manufacturing speeds. This problem is believedto be characteristic of relatively pliable strip-like materials. Withoutintending to be bound by theory, it is believed that for any particularstrip-like material, the problem increases along with increasingwidth-to-thickness ratio (cross-sectional aspect ratio). It is believedthat the problem may begin to become significant with pliable materialsof the nature discussed herein when they have cross-sectional aspectratios of approximately 2.5 or greater. As cross-sectional aspect ratiofor a given material increases, the problem becomes more significant. Itis believed that the problem also becomes more significant withincreasing pliability across the width of the material (increasingflexibility along longitudinal lines). It is also believed that theproblem becomes more significant with a decrease of longitudinal tensionin the material. Additionally, air resistance/friction may contribute toroping when attempting to rapidly shift a free span of strip materiallaterally through open air at required manufacturing speeds. If a freespan of pliable strip material is shifted laterally at high enoughspeeds through open air, friction with the air may cause the span totwist and/or rope erratically. If strip material 42 is roped as itenters a joining mechanism to be affixed to backsheet material 50,non-uniform leg bands having defects in width, thickness, placement,feel and/or appearance are among several possible undesirable results.

A combination of manufacturing line components including a guideupstream of a joining mechanism that urges and affixes a strip materialand a substrate sheet material together, is described below. Thecomponents also may include a mechanism for regulating the strain in thestrip material as it enters the joining mechanism. It is believed thatcomponents in the combination, and the combination, are embodiments ofcomponents and a system that may be effective at continuously affixingstrip material to substrate sheet material at laterally varyinglocations relative to the machine direction, at speeds that may berequired for manufacturing, while reducing or avoiding the problem ofroping of the strip material described in more detail above. Embodimentsof the strain regulation mechanism described may enable effectiveregulation of the strain in the strip material as it is affixed to thesubstrate sheet material.

Example of Combination of Manufacturing Line System and Components forLocating and Affixing Strip Material to Sheet Material

FIG. 4 is a perspective drawing depicting an example of an arrangementof manufacturing line components. The components may include at leastone servo motor 150 having rotatable drive shaft 151. Strip guide arm100 may be mounted to drive shaft 151 via coupling collar 109. Couplingcollar 109 may have drive shaft cavity 112 therein (further describedbelow and depicted in FIGS. 6B, 6D), to receive the end of drive shaft151.

Coupling collar 109 may be mounted to the end of drive shaft 151 in anysuitable manner that prevents substantial rotational slippage/movementof strip guide arm 100 relative to drive shaft 151, including, forexample, by welding, press-fitting, keying, splining, set screw(s), etc.However, welding and other devices for mounting that involve potentialalteration, modification, damage or destruction to draft shaft 151and/or servo motor 150 may in some circumstances be deemed undesirablefor reasons that may include added complexity and expense of systemassembly, and potential complication or frustration of replacement of aworn or broken strip guide arm 100 without having to also repair orreplace servo motor 150. Devices such as set screws may be unreliable inthat stress and vibration during operation may cause them to work looseor fail. Thus, one example includes a taper locking collar as a devicefor mounting coupling collar 109 to drive shaft 151. A suitable exampleof such a taper locking collar is a TRANTORQUE keyless bushing availablefrom Fenner Drives, Leeds, UK.

Examples of suitable servo motors include servo motors designatedMPL-B330P and MPL-B4560F, available from Rockwell Automation, Inc.,Milwaukee, Wis. The programming of the selected servo motor, to effectlateral location of the strip material 42 relative to backsheet material50 and create the partially completed portion 51, will be directed bythe particular article design.

A strip guide 102 may be situated at a downstream location on stripguide arm 100. The components may be arranged such that strip guide 102is upstream of a joining mechanism 200. In the example shown in FIG. 4,joining mechanism 200 may include first and second joining rollers 201,202 that rotate about axles 203, 204 situated along substantiallyparallel axes. Examples of suitable joining mechanisms utilizing rollersare described in, for example, U.S. Pat. Nos. 4,854,984 and 4,919,738,issued to Ball et al. In these types of mechanisms, a first joiningroller 201 may have on its surface one or more protuberances ofsubstantially uniform height arranged in one or more lines or patterns.First joining roller 201 and second joining roller 202 may be urgedtogether by one or more actuators such as bellows-type pneumaticactuators 205 acting directly or indirectly on one or both of axles 203,204, to provide and regulate compression under the protuberances ofstrip and sheet materials passing together through the nip between therollers, in the manner described in the aforementioned patents.

A joining mechanism utilizing compression as the primary means ofcreating bonds, such as, but not limited to, the mechanism described inthe aforementioned patents, provides bonding of respective sheet-like orstrip-like polymeric materials through rapid compression of therespective materials together beneath the protuberances, along theroller nip line. Without intending to be bound by theory, it is believedthat rapid compression beneath the protuberances causes the respectivematerials to be rapidly deformed and partially expressed together frombeneath the protuberances, to form structures of entangled or combinedmaterial beneath and/or around the protuberances. Welds or weld-likestructures at or about the protuberances result. In some circumstancescompression bonding provides advantages, including relative simplicityand cost effectiveness. It may reduce or eliminate the need for morecomplex joining and bonding systems that rely upon, for example,adhesives and mechanisms to handle and apply them, or weld-bondingsystems that require a heat source, ultrasonic wave source, etc. Withoutintending to be bound by theory, it is believed that these advantagesare substantially independent of variations in line speeds in at leastsome circumstances, including line speeds within currently knowneconomically and technically feasible ranges for manufacture ofdisposable diapers and training pants.

FIG. 5 is a schematic depiction of how an arrangement of components suchas that shown in FIG. 4 may be operated to affix a strip material to asubstrate material. Substrate backsheet material 50 and one or morestrips of strip material 42 may be drawn longitudinally from respectivesupplies 60, 61 toward joining mechanism 200 in the respective machinedirections indicated by the arrows. Strip material 42 as selected forthe particular application may have a cross-sectional aspect ratio suchas that described in the preceding example of a wearable article.Joining mechanism 200 may include first and second joining rollers 201,202. Upstream of joining mechanism 200, the one or more strips of stripmaterial 42 move along one or more strip guide arms 100. As they movealong the strip guide arms 100, strips of strip material 42 may beslidably retained at upstream and downstream locations on strip guidearms 100 by, respectively, strip retainer extensions 110 and stripguides 102. The system may be designed and equipped to providecompression bonding of strip material 42 to backsheet material 50 asnoted above. In another example, an adhesive may be applied to stripmaterial 42 upstream of joining mechanism 200, and joining mechanism 200may press strip material 42 against substrate backsheet material 50 toform an adhesive bond therebetween. In this latter example, joiningmechanism 200 also may comprise joining rollers 201, 202, which serve tourge and compress strip material 42 and backsheet material 50 togetherto form the adhesive bond.

Referring to FIGS. 4 and 5, the one or more strip guide arms 100 mayhave coupling collars 109 mounted to the rotatable drive shaft(s) 151 ofone or more servo motors 150. The one or more servo motors 150 may beoperated by suitable programming to pivot guide arms 100 back and forthsuch that strip guides 102 move laterally (in respective arcs alongpaths of rotation) across the machine direction, to cause strip material42 to be laterally shifted and varyingly located with respect to themachine direction of the substrate backsheet material 50 as it entersthe joining mechanism 200, as required by the article design. Joiningmechanism 200 then may affix strip material 42 to backsheet material 50at the required locations, resulting in a completed portion 51 (alsoshown in FIG. 3 and described above) exiting joining mechanism 200 andmoving downstream for further manufacturing steps.

The one or more servo motors 150 may be situated such that the arc pathsof strip guides 102 occurs within in one or more planes. If thecomponents are arranged such that the arc path of a strip guide 102 issubstantially parallel with the plane which contains the nip linebetween joining rollers 201, 202, one mode of variation in the angle atwhich the strip material enters the nip is eliminated. Without intendingto be bound by theory, it is believed that control over lateral shiftingof the strip material and/or avoidance of roping are simplified and/orimproved by such an arrangement.

Strip Guide and Guide Arm

An example of a strip guide 102 is depicted in perspective, side, frontand rear views in FIGS. 6A, 6B, 6C and 6D, respectively. Strip guide 102may be situated at or near the downstream end of strip guide arm 100.Strip guide arm 100 may extend from coupling collar 109.

In the example shown, strip guide 102, strip guide arm 100, and couplingcollar 109 may be formed of aluminum alloy, and also may be integrallyformed. Materials having a relatively high strength-to-weight ratio maybe desirable in some circumstances. Examples of other suitable materialsmay include engineering plastics (such as polycarbonate thermoplastics,for example, LEXAN), aluminum, titanium alloys, thermoplastic orthermosetting resins reinforced with carbon fibers, graphite fibers,polyamide fibers, metal fibers and/or glass fibers, or other carbonfiber, graphic fiber, polyamide fiber, metal fiber and/or glass fibercomposites.

Referring to FIGS. 6A and 6C, it can be seen that strip guide 102 may beformed to have an inner surface defining a U-shape, across which surfacethe strip material moves longitudinally. For purposes of thisdescription, the term “U-shape” is to be broadly construed to includeany two-dimensional figure lying within a plane with respect to a linewithin the plane, having either an intermediate straight portion alongthe line, or an intermediate curved portion to which the line istangent, and two side portions each lying within the plane and on thesame side of the line, and each extending from the intermediate portionin one or more directions away from the line. Where the intermediateportion is curved, the side portions may be continuous or discontinuouswith such curve; thus, for example, an arc forming any portion of acircle falls within the definition of “U-shape” herein. By way offurther example, the term includes a “C” shape, trough or open channelcross-sectional shape, horseshoe shape, etc. Unless otherwise specifiedthe side portions need not terminate at a point of discontinuity. Thus,the term also includes, unless otherwise specified, any portion of aclosed figure such as but not limited to a circle, oval, ellipse,rectangle, square, etc., that satisfies the foregoing definition.Symmetry about any particular axis is not intended to be implied orrequired unless otherwise specified. No limitation as to the spatialorientation of the U-shape with respect to other components of thesystem is implied or intended; for example, within the system theU-shape may be upside-down with respect to the letter “U”; see, e.g.,strip guides 102 in FIG. 5.

Referring to FIG. 6C, in the example shown, the U-shape may have anintermediate portion 103 that substantially defines a semicircle, andtwo substantially straight side portions 104 a, 104 b. Without intendingto be bound by theory, it is believed that an intermediate portion 103of such shape may be more effective than other possible U-shapes for thepurposes contemplated herein. It is believed that such substantiallysemicircular shape provides for easier and smoother lateral movement ofstrip material from side to side within strip guide 102 as strip guidearm 100 pivots back and forth during operation, allowing for bettercontrol over lateral shifting of the strip material, and bettercapability to prevent roping, than may be achieved with other possibleshapes.

Still referring to FIG. 6C, strip guide 102 may have first and secondstrip edge stops 105 a, 105 b substantially terminating, or constitutingsubstantially abrupt discontinuities, on side portions 104 a, 104 b.First and second strip edge stops 105 a, 105 b may extend from sideportions 104 a, 104 b and inwardly toward each other, and may terminateat points short of each other to leave downstream strip insertion gap108. First and second strip edge stops such as those shown at 105 a, 105b may serve to retain a strip material within strip edge guide 102during operation, preventing it from riding all the way up and off aside portion, and out of the strip guide.

Referring to FIG. 7, in another example strip guide 102 may have firstand second strip edge guides 106 a, 106 b substantially terminating, orconstituting substantially abrupt discontinuities, on side portions 104a, 104 b. First and second strip edge guides 106 a, 106 b may extendfrom the ends of side portions 104 a, 104 b, inwardly toward each other,then toward intermediate portion 103, and then may terminate at pointsshort of intermediate portion 103. In the example shown in FIG. 7, aswith the example shown in FIG. 6A, there may be a downstream stripinsertion gap 108 between first and second strip edge guides 106 a, 106b. First and second strip edge guides such as those shown at 106 a, 106b may serve to retain a strip material within strip edge guide 102during operation, and also may be effective for providing additionalassurance that longitudinal edges of a strip material do notlongitudinally fold or flip over (rope) as the strip material shifts andrides up a side portion 104 a, 104 b during operation. The stripclearance 107 a, 107 b between the respective side portions 104 a, 104 band respective strip edge guides 106 a, 106 b may be optimized to avoidunduly increasing friction resistance to longitudinal movement of thestrip through the strip guide 102, while still having the desired effectof preventing the strip from roping. For example, if the strip materialto be used is 2 mm thick, the strip guide 102 such as shown in FIG. 7might be formed to have strip clearance 107 a, 107 b of, for example,approximately 2.5-3.5 mm.

Without intending to be bound by theory, it is believed that a stripguide such as strip guide 102 having strip edge guides such as thoseshown at 106 a, 106 b (FIG. 7) is more effective at preventing roping ofstrip than other embodiments lacking such strip edge guides. However, ifthe system for affixing the strip material to the substrate involvesapplication of adhesive to the strip material upstream of the stripguide 102, edge guides wrapping over as shown might be deemed unsuitablein some circumstances, if they could become fouled with adhesive as thestrip passes through the strip guide, or otherwise, could collectdeposits of adhesive from the strip and randomly release them back ontothe strip in unintended locations. Conversely, a strip guide havingstrip edge guides wrapping over, such as strip edge guides 106 a and 106b, may be desirable in some circumstances, possibly such as when thesystem does not apply adhesive to the strip upstream of the strip guide.

As shown in the examples depicted in FIGS. 6A-6D and 7, at the upstreamend of strip guide arm 100, two strip retainer extensions 110 mayproject from the edges of trough 101 inwardly toward each other,terminating short of each other to leave upstream strip insertion gap111. Coupling collar 109 may have a substantially cylindrically-shapeddrive shaft cavity 112 therein, as is indicated by dashed lines in FIGS.6B and 6D.

The upstream and downstream strip insertion gaps 111, 108 provide forease of lateral insertion of the strip material to be used into andalong strip guide arm 100 during set-up. In another example, however,the respective strip retainer extensions 110 may be formed to meet, orbe continuous to effectively constitute a single retainer structure,whereby the strip material must simply be longitudinally threadedthereunder, rather than laterally inserted through a gap, at set-up.Similarly, strip edge stops 105 a, 105 b (FIG. 6C) or strip edge guides106 a, 106 b (FIG. 7) may be formed to meet, or be continuous, toeffectively constitute a single strip retainer structure, whereby thestrip material must simply be longitudinally threaded thereunder, ratherthan laterally inserted through a gap, at set-up.

As previously noted, without intending to be bound by theory, it isbelieved that a strip guide 102 may be more effective than otherembodiments for the purposes contemplated herein if it includes anintermediate portion 103 (see, e.g., FIG. 6C) that substantially definesa semicircle. Without intending to be bound by theory, it is furtherbelieved that for the strip guide 102 to be more effective than otherpossible embodiments, the semicircle may have a radius r₄ of a lengththat is approximately 21-43 percent of the width of the strip material,or approximately 26-38 percent of the width of the strip material, orapproximately 30-34 percent of the width of the strip material, or evenapproximately 32 percent of (or approximately (1/π) times) the width ofthe strip material to be used. If r₄ is a length that is approximately32 percent of (or approximately (1/π) times) the width of the stripmaterial to be used, the linear length of the arc formed by thesemicircle is approximately equal to the width of the strip material. Itis believed that a radius r₄ falling within one or more of these rangesmay optimize the effect of the strip guide upon orientation of therespective longitudinal side edges of a strip as it enters the nipbetween a roller pair, striking a balance between most effective controlover lateral shifting and minimizing the likelihood of roping andcontour error.

Additionally, without intending to be bound by theory, it is believedthat a strip guide 102 may be more effective if it has at least one sideportion 104 a and/or 104 b joining the intermediate portion 103, thanother possible embodiments not having such a side portion, for purposessuch as those described herein. A side portion joining the intermediateportion at a side opposite the direction of lateral motion of the stripguide may provide additional guiding surface against which a stripmaterial may ride during abrupt and/or severe changes in lateralposition of the strip guide. The side portion may be substantiallystraight, and may be of a length that is approximately 21-61 percent ofthe width of the strip material, or approximately 26-56 percent of thewidth of the strip material, or approximately 30-52 percent of the widthof the strip material, or even approximately 32-50 percent of the widthof the strip material to be used. It is believed that such a dimensioncauses optimization of the orientation of the respective longitudinalside edges of a strip as it enters the nip between a roller pair,striking a balance between most effective control over lateral shiftingand minimizing the likelihood of roping and contour error.

It is further believed that embodiments having two such side portionsare more effective than embodiments with only one side portion,particularly if the strip material is to be shifted laterally to bothsides of a line of entry of the strip material at the upstream end ofthe strip guide arm 100 (e.g., at upstream entry point 113). Expresseddifferently, when strip guide 102 is to move back and forth to points onboth sides of the line of entry of the strip material at upstream entrypoint 113, two such side portions 104 a, 104 b may be desirable in somecircumstances to improve control over the strip material.

During operation, as the strip guide 102 moves toward the limit of itslateral arc path to shift the strip laterally, the strip exits the stripguide at an increased lateral angle, creating a potential for frictionlock, i.e., a point of unacceptably concentrated friction between thestrip and the strip guide at the exit point as a result of tension inthe strip. To mitigate this problem, in addition to having theabove-described features, it may be desirable in some circumstances toshape the inside distal edges of the strip guide 102. The inside distaledges may be shaped such that they are chamfered, rounded or radiused,or even given a quarter-round transition, from inside surface to outsideedge, to reduce friction between the strip guide 102 and the stripmaterial as it passes longitudinally therethrough and exits thedownstream end.

As noted, in the example shown strip guide 102 may be integrally formedwith strip guide arm 100. Referring to FIG. 6A, strip guide arm 100 mayform a trough 101, which on its inside surfaces may conform to theabove-described U-shape at the downstream end, and gradually flatten outas it approaches the upstream (strip entry) end where strip guide arm100 joins coupling collar 109. In another example, the strip guide armmay form a trough that does not substantially flatten out, but rather,has a depth from the strip guide to the upstream strip entry end, whichmay be substantially continuous. Because strip arm 100 may pivot backand forth such that strip guide 102 moves in an arc path back and forthabout an axis (see FIG. 5) at a rate of approximately, for example, 7.5cycles or more per second, a trough or other channel, conduit, tube orother suitable containing or retaining structure along the length ofstrip guide arm 100 may serve to contain the length of strip material 42present along the length of strip guide arm 100 during such movement.Thus, such structure may provide additional inside surface areatherealong that may serve to exert lateral force against strip material42, working against the inertia or counter-momentum of the stripmaterial and reducing a concentration of friction or binding of stripmaterial 42 that may occur at strip guide 102 as strip guide 102 movesback and forth to effect rapid lateral shifting. Reduction ofconcentrations of friction may be desirable to reduce or avoid possibleinconsistencies in the longitudinal strain of the strip material 42 asit is drawn into the joining mechanism.

Additionally, a trough or other channel, conduit, tube or other suitablecontaining, retaining and/or shielding structure along strip guide arm100 may serve to shield the strip material from surrounding air and theresistance to lateral movement of the strip material 42 therethrough.Absent a shielding structure, friction with surrounding air may cause afree span of a typically pliable and relatively light, cloth-like stripmaterial 42 to erratically and uncontrollably flip about and rope as thestrip material is rapidly shifted laterally by strip guide 102.

In another example of a possible alternative to the upstream strip entrypoint 113 depicted in the Figures, the strip guide arm may have aupstream strip entry guide similar in design to the strip guide 102 butoriented in the opposite direction. This may provide further assuranceagainst roping of the strip material. It also may serve to prevent orreduce increased friction or binding at the entry of strip material 42into/onto strip guide arm 100 when strip guide arm pivots and introducesa varying angle in the path of the strip material, about the strip entrypoint. Again, avoidance or reduction of a concentration of friction atany particular point is desirable to avoid inconsistencies in thelongitudinal strain of the strip material 42 as it is drawn into thejoining mechanism.

It may be desirable in some circumstances that one or more of thesurfaces of the strip guide 102, and other surfaces in or along stripguide arm 100 that contact the moving strip material, be polished toreduce friction between the strip material and such surfaces. This mayinclude any of the inner surfaces of trough 101, strip edge stops 105 a,105 b, strip edge guides 106 a, 106 b, strip entry point 113, stripretainer extensions 110, and any intermediate strip-contactingstructures.

In addition, or as another possible measure, one or more of thesesurfaces may be coated with a low-friction coating, such as, forexample, a fluoropolymer-based coating such as TEFLON, a product of E.I. du Pont de Nemours and Company, Wilmington, Del. Relative to thecoefficient of friction provided by the strip guide/strip guide armmaterial without a coating, any suitable coating that lowers thecoefficient of kinetic friction with the material of the outer surfacesof the strip material to be used may be selected. In another example,where an adhesive is to be applied to the strip material upstream of thestrip guide arm 100 and/or strip guide 102, it may be desirable to coatstrip-contacting surfaces of the strip guide arm 100 and/or strip guide102 with an adhesive release coating. In another example, one or moreinserts of a low-friction material conforming to the desiredstrip-contacting surface shape may be affixed on or within strip guide102, strip guide arm 100, trough 101, strip edge stops 105 a, 105 b,strip edge guides 106 a, 106 b, strip entry point 113, strip retainerextensions 110, and any intermediate strip-contacting structures. Suchinserts may be formed in whole or in part of low-friction materials suchas, but not limited to, nylon, high density polyethylene, andfluoropolymer-based materials such as TEFLON.

In another example, a strip guide arm 100 and strip guide 102 may havesome or all of the features and spatial arrangement with respect to ajoining mechanism 200 as described above. However, rather than beingconnected to a servo motor, strip guide arm 100 may be connected at apivot point to a stationary component, about which pivot point the stripguide arm 100 may pivot back and forth. In this example, strip guide arm100 also may include a cam follower as part thereof, or connectedthereto, which rides on a rotating cam directly or indirectly driven bya rotating driving mechanism, such as a rotary electric motor. The camfollower may be urged against the cam by any appropriate biasingmechanism, such as, but not limited to, one or more springs. The cam maybe formed to have a profile such that by its rotation, strip guide arm100 pivots as required to laterally shift strip material as required forthe article being manufactured. The rotating driving mechanism may beoperated so as to rotate the cam at a speed which is suitably associatedwith the speed at which the substrate material is moving.

In another example, a strip guide 102 having some or all of the featuresdescribed above may be employed without a strip guide arm, servo motor,or the rotary operation described above. Rather, a strip guide may beconnected to a linear movement mechanism such as, for example, a linearmotor or actuator arranged to move the strip guide 102 along a lineupstream and substantially parallel to the nip line between joiningrollers 201, 202.

Additional Strip Guide Design Features; Strip Guide Arm Dimensions,Location and Orientation

Referring to FIGS. 8 and 9, where a joining mechanism including rollerssuch as first and second joining rollers 201, 202 is used, decreasingthe distance between strip guide 102 and the nip line 206 betweenjoining rollers 201, 202 sharpens the possible angle α (the anglereflecting a lateral break in the line of placement of the stripmaterial 42 on a substrate material relative to the machine direction(see, e.g., FIG. 3), that can be achieved. Constraints on closeness ofthis distance may include the physical dimensions of the servo motor andjoining mechanism/rollers used and limits on the length of the stripguide arm, discussed further below. If a joining roller 201, 202 has aradius of about 7.62 cm, it may be desirable in some circumstances toarrange the components so that the distal edge of strip guide 102 isless than about 2 cm from nip line 206. Depending upon features andsizes of the components used, it may be possible in some circumstancesto arrange the components such that the ratio of the distance betweendistal edge of strip guide 102 and the nip line to the radius of thesmaller of the rollers that strip guide 102 faces, is less than about0.34, or less than about 0.31, or less than about 0.29, or even lessthan about 0.26.

As the arranged distance between the distal edge of strip guide 102 andthe nip line is decreased as constraints permit, it may become desirablein some circumstances to form strip guide 102 so as to have a radiusedconcave profile as viewed from a side, having radius r₃ (see FIG. 6B).Radius r₃ may originate at the axis of one of first or second joiningrollers 201, 202, such that the concave side profile of strip guide 102is concentric with the joining roller 201 or 202 that it faces. Thisenables the distal tip of the strip guide 102 to be located closer tothe nip line, while avoiding interference between the other portions ofthe strip guide 102 and the roller it faces.

Under certain circumstances forces created by air entrainment or otherfactors may tend to lift strip material 42 from the inner surfaces ofstrip guide 102, reducing the efficacy of strip guide 102. Stillreferring to FIGS. 8 and 9, it may be desirable in some circumstances toarrange servo motor 150 with mounted strip guide arm 100 such that stripmaterial 42 passing along strip guide arm 100 forms a first break angleφ₁ between its path along strip guide arm 100 and its path from stripguide 102 to the nip line between joining rollers 201, 202 (see FIG. 8).First break angle φ₁, combined with tension in the strip material 42,may help assure that strip tension-related forces urge strip material 42into strip guide arm 100 and strip guide 102 (downwardly with respect toFIG. 8), and hold strip material 42 against the inside surfaces thereof.For similar reasons, it may be desirable in some circumstances toarrange a servo motor 150 with mounted strip guide arm 100, and/or thesupply source of strip material 42, such that strip material 42 passingalong strip guide arm 100 forms a second break angle φ₂ between its pathfrom the upstream strip material feed (e.g., feed rollers 301, 302) andits path along strip guide arm 100 (see FIG. 8). In one example, secondbreak angle φ₂ may be designed into and formed as a feature of stripguide arm 100, trough 101 thereof and/or the interface between upstreamstrip entry point 113 and trough 101. One or both of break angles φ₁ andφ₂ may be kept within a range of about 135-179 degrees, or about 151-173degrees, or about 159-170 degrees, or even about 167 degrees. Withoutintending to be bound by theory, it is believed that, depending uponfactors which may include the coefficient of kinetic friction betweenthe strip material and the strip guide surfaces, a break angle φ₁ or φ₂smaller than about 135 degrees may be too sharp, i.e., it could possiblyresult in an unacceptable concentration of friction between stripmaterial 42, strip guide 102 and/or upstream strip entry point 113 asstrip material 42 passes thereover. Further, without intending to bebound by theory, it is believed that optimization of break angles φ₁ andφ₂ will be affected by the modulus of elasticity of the strip material,the longitudinal strain or tension in the strip material as it passesalong strip guide arm 100, the lateral stiffness or “beam strength” ofthe strip material, the width of the strip material, and the linearspeed of the strip material as it passes along strip guide arm 100.

Referring to FIG. 10, in another embodiment and as an alternative tobeing formed and arranged to create discrete break angles φ₁ and φ₂,strip guide arm 100 may be designed and formed so as to provide acurving strip guide arm path 114 therethrough, which diverges away (withreference to FIG. 10, downwardly) from the incoming strip material pathwhen the other components are appropriately arranged. The components maybe arranged such that the total break angle φ₃ between the incomingstrip path (upstream of where strip material 42 contacts strip guide arm100) and the exiting strip path (downstream of where strip materialbreaks contact with strip guide 102) is from about 90-178 degrees, orabout 122-166 degrees, or about 138-160 degrees, or even about 154degrees. Such a total break angle φ₃, combined with tension in the stripmaterial, may help improve the likelihood that strip tension-relatedforces urge strip material 42 against inside surfaces of the describedcurving strip guide arm path 114 (with reference to FIG. 10, along thebottom surfaces inside strip guide arm 100).

In some circumstances it may be desirable that the length of the stripguide arm 100 is as great as possible. As the strip guide arm 100 ismade longer, the arc path of the strip guide 102 in front of nip line206 approaches that of a line. As such a linear path is approached, thepotential sharpness of a lateral shift of the strip material in front ofthe nip line is increased. However, the torque load capacity of anyservo motor, and the material strength of any strip guide arm, will havelimits. These factors are sources of constraints on the design length ofthe strip guide arm 100. Torque load on the servo motor in thearrangement of components described herein will be at its maximum whenthe most rapid change in direction and/or speed of rotation (highestangular acceleration/deceleration) is imposed by the design of thefinished product (i.e., the most abrupt angularacceleration/deceleration required of the strip guide arm will imposethe greatest torque load). If the torque load capacity of a servo motoris exceeded, the precision of rotation of the servo motor drive shaftmay deviate unacceptably from that required by the associatedprogramming, and the servo motor may even fail. Additionally, as a stripguide arm 100 mounted to the drive shaft of a servo motor is made longerand/or heavier along its length, angular inertia and angular momentumbecome greater. As a result, angular acceleration/deceleration requiregreater torque, imposing greater demand on the servo motor.Bending/shear stress along the length of the strip guide arm alsoincreases with increasing angular acceleration/deceleration and angularinertia/momentum, increasing the probability of strip guide arm materialfailure. Related constraints are imposed by the line speed and theresulting cycling speed demanded of the servo motor, and by themagnitude and abruptness of the change in lateral placement of the stripmaterial, a function of the design of the article being manufactured.Another related constraint is imposed by the weight of the stripmaterial that is being handled by the strip guide arm, which adds tolateral inertia and momentum which must be overcome to effect lateralshifting. Many or all of the above-discussed design considerations willbe affected by the particular design of the article to be manufactured,which will involve a particular profile of location and affixation of astrip material to a substrate material at laterally varying locations onthe substrate material.

Effects of Described Components and Features

Certain effects and advantages provided by components and featuresdescribed above are discussed with reference to FIGS. 11A-11D. FIG. 11Aillustrates a strip guide arm 100 with strip guide 102 situated at thedistal end thereof (similar to that shown in FIGS. 6A-6D) having stripmaterial 42 threaded therethrough, these components representedisolated, but otherwise as they might appear in a system within thescope of present invention. FIG. 11A depicts an arrangement with asubstantially straight strip path (viewed from above) from point a topoint b. When the path of strip material 42 as viewed from above issubstantially straight, pliable strip material 42 enters proximal entrypoint 113 in substantially flat condition, then gradually flexes acrossits width so as to rest in concave fashion in and against the surfacesof the intermediate portion of strip guide 102. In FIG. 11B, strip guidearm 100 is shown pivoted clockwise by an angle θ, as it might be pivotedin operation in a system in order to effect lateral shifting of stripmaterial 42. With pivoting of strip guide arm 100, strip material 42tends to move and ride up along the side portion 104 b that is situatedopposite the direction of rotation (relative to FIG. 11B, to the rightof strip guide 102). Correspondingly, the right edge of strip material42 (relative to FIG. 11B) is raised and the left edge is lowered. Thestrip material does not tend to rope.

FIGS. 11C and 11D are views of the strip guide arm 100 shown in FIGS.11A and 11B from the opposite perspective of that of FIGS. 11A and 11B,as strip guide arm 100 may appear operating as a component of a system.FIGS. 11C and 11D show how strip guide 102 affects entry of the stripmaterial 42 into the nip 206 between joining rollers 201, 202. In FIG.11C, the path of strip material 42 moving toward joining rollers 201,202 is substantially straight, as in FIG. 11A. As it moves along stripguide arm 100 and through strip guide 102, strip material 42 may beurged by the inside surfaces of strip guide arm 100 and/or strip guide102 into a concave shape across its width, and may enter the nip betweenjoining rollers 201, 202 with each of its side edges upturned (withrespect to the view in FIG. 11A). However, roping of strip material 42may be avoided, and strip material 42 is then flattened against thesubstrate as it passes through the nip. Referring to FIG. 11D, whenstrip guide arm 100 pivots clockwise and strip guide 102 moves to theright (relative to FIG. 11D), strip material 42 may shift to the left ofthe strip guide 102, riding up the left inside surface and up sideportion 104 b of strip guide 102. Strip material 42 may approach the nipbetween joining rollers 201, 202 in a concave shape across its width,with its left side edge higher and its right side edge lower (withrespect to the view in FIG. 11C). As a result, the upturned left sideedge may contact upper joining roller 201 before the remaining width ofthe strip does, but then be urged down and flattened by joining roller201 as the strip material 42 enters the nip. Strip guide 102 acting incombination with the joining rollers 201, 202, may thereby enable stripmaterial 42 to be drawn into and compressed at the nip without roping.Thus, strip material 42 may be caused to emerge from the downstream sideof the nip affixed to the substrate material in a flat condition.

Thus, a system having one or more of the features described above may beused to manufacture a portion of wearable article such as that shown inFIG. 1, having respective leg openings circumscribed by legbands 40,each formed of a single length of elastic strip material, whichsubstantially encircles its leg opening. The backsheet 20 may comprise anonwoven web material. For each legband 40 the single length of elasticstrip material encircling the same may be bonded to the nonwoven webmaterial via compression bonding.

Strip Strain Regulation

As previously noted, in one example of a design of a product such aswearable article 10 and the manufacture thereof, the design may call forthe longitudinal straining of the strip material prior to the affixingthereof to a substrate sheet material. In some circumstances it may bedesirable to provide a system for introducing and regulating the amountof strain of the strip material prior to its entry into a joiningmechanism.

An example of a strain regulation system is schematically depicted inFIGS. 12 and 13. The example may include the joining mechanism 200 withfirst and second joining rollers 201, 202, and a strain regulationmechanism 300 that may include first and second feed rollers 301, 302.Feed rollers 301, 302 may substantially non-slippably draw and feedincoming strip material 42 in a downstream direction as indicated by thearrows. One or both of feed rollers 301, 302 may have a circumferentialsurface of a compressible elastic material such as a natural orsynthetic polymeric material, for example, rubber. This may help avoiddamage to the strip material 42 (from compressing it beyond the limitsof its elasticity) as it passes through the nip between feed rollers301, 302. Additionally a rubber or rubber-like material may be providedthat provides a coefficient of friction between the strip material 42and the feed roller surface that is sufficient to avoid longitudinalslippage of the strip material 42 through the nip. It may be desirablein some circumstances to locate feed rollers 301, 302 as closely aspossible to upstream strip entry point 113. This will minimize theoverall length of the path of the strip material 42 from the nip betweenfeed rollers 301, 302 to the joining mechanism, and thus, facilitatemore precise control over strain in the strip material 42.

To longitudinally strain incoming strip material 42 prior to bonding toincoming backsheet material 50, feed rollers 301, 302 may be caused torotate at a speed whereby the linear speed of the circumferentialsurfaces of feed rollers 301, 302 is slower than the linear speed of thecircumferential surfaces of joining rollers 201, 202 of joiningmechanism 200. If r₁ is the radius of feed roller 301 (in meters) and ω₁is the rate of rotation of feed roller 301 (in rotations/second), thelinear speed V₁ of its circumferential surface is:

V₁=2πr₁ω₁ meters/second,

which will be the linear strip feed speed through the nip between feedrollers 301, 302.

Similarly, if r₂ is the radius of joining roller 201 (in meters) and ω₂is the rate of rotation of joining roller 201 (in rotations/second), thelinear speed V₂ of its circumferential surface is:

V₂=2πr₂ω₂ meters/second,

which is the linear strip draw speed through the nip between rollers201, 202.

Strain will be introduced into the strip material 42 if V₁ is less thanV₂ and strip material 42 does not substantially slip longitudinally asit passes through the respective nips between respective roller pairs301, 302 and 201, 202. Thus, referring to FIG. 12, strip material 42 maybe drawn from zone “A” in a substantially non-strained condition by feedrollers 301, 302 at a linear feed speed slower than the linear stripdraw speed of joining rollers 201, 202. As a result, the strip material42 in zone “B” will be strained prior to its entry into joiningmechanism 200.

Thus, if a design for an article calls for longitudinally straining thestrip material to strain ε(ε=change in length/relaxed length; where ε isexpressed as a percentage) prior to bonding to the substrate material,relative speeds V₁ and V₂ will provide for the required strain ε if:

(1+ε)V ₁ =V ₂, or

V ₂ /V ₁=(1+ε),

assuming a constant length of the path of the strip material from thefeed mechanism to the joining mechanism. Accordingly, for example, toimpart 70% strain to the strip material as it is affixed to a substratematerial, the respective feed rollers 301, 302 and joining rollers 201,202 may be operated such that V₂/V₁=1.70, assuming a constant length ofthe path of the strip material from the feed mechanism to the joiningmechanism.

In the event, however, that the length of the path of the strip materialfrom the feed mechanism to the joining mechanism is subjected to change,strain of the strip material in zone “B” will undergo an associatedtransient elevation or dip. If the change in path length is substantialand abrupt enough, it is possible that the strain in the strip materialmay be caused to transiently elevate or dip substantially. Examples of asystem as described herein shift a strip material path laterally priorto its entry into a joining mechanism, to cause affixation of the stripmaterial to a substrate material in laterally varying locations on thesubstrate material. This lateral shifting causes change in the length ofthe path of the strip material from the feed mechanism to the joiningmechanism. A change of this nature may be substantial and abrupt enoughto substantially vary strain of the strip material in zone “B”.

FIGS. 13 and 14 show that the path of the strip material 42 fromupstream strip entry point 113 to first nip point 206 a has a first pathlength in zone “B” when strip guide arm 100 is oriented with itslongitudinal axis substantially perpendicular to nip line 206. The firstpath length is approximately the sum of the length L of strip guide arm100 plus distance d₀ from strip guide 102 to nip point 206 a.

Pivoting of strip guide arm 100 by an angle θ causes an increase in thepath length. The increase reaches an initial peak in the path length,which approaches the sum of strip guide arm length L plus the distanced₁ from strip guide displacement point D to first nip point 206 a, asspeed of rotation by angle θ approaches infinity (pivoting of arm 100approaches instantaneous). The increase then settles back from theinitial peak to a second path length, as the nip point between joiningrollers 201, 202 shifts as indicated by the arrow in FIG. 14 from firstnip point 206 a to second nip point 206 b by continuing rotation ofjoining rollers 201, 202. The second path length will be approximatelythe sum of strip guide arm length L plus the distance d₂ from stripguide displacement point D to second nip point 206 b. The second pathlength, while less than the peak, remains greater than the first pathlength.

With V₁ and V₂ held constant, a path length increase will notnecessarily cause a substantial elevation in strain. Through thecontinuous feeding and drawing of strip material through zone “B” byroller pairs 301, 302 and 201, 202, the system continuously corrects anelevation or dip in strain, always asymptotically seeking the straindetermined by the values of V₁ and V₂ (see equations immediately above).Accordingly, in some circumstances the system may effectively regulateand maintain substantially consistent strain despite changes in pathlength. The time required for the system to substantially correct atransient elevation in strain resulting from an increase in path lengthis dependent upon the total length of the strip material path in zone“B” and the values of V₁ and V₂. Thus, if pivoting of strip guide arm toangle θ is relatively slow and gradual, the system may be able toeffectively “keep up,” continuously seeking initial strain, and anytransient elevation in strain may be relatively slight.

As the pivoting of strip guide arm by angle θ becomes more rapid,however, the system may become unable to effectively “keep up” andmaintain strain within an insubstantial margin of elevation over initialstrain. Thus, it is possible that a relatively rapid pivoting of stripguide arm through angle θ may cause a substantial elevation in thestrain of strip material in zone “B”.

The foregoing describes only one possible example of circumstances inwhich strain in strip material 42 may vary as a result of a change inpivot angle θ. There may be other circumstances in which elevations andeven dips in strain may be caused. For example, still referring to FIGS.12-14, there may be circumstances in which pivot angle θ is at amaximum, the nip point is at 206 b, and the system has stabilized toinitial strain. If pivot angle θ is then decreased, the decrease willcause a dip in the strain in the strip material in zone “B” below itsinitial value as strip guide 102 moves past nip point 206 b, followed byan elevation as strip guide 102 moves away from nip point 206 b(downwardly with reference to FIGS. 13 and 14). Again, if the pivotingof the strip guide arm through these positions is relatively rapid, thecorresponding dip or elevation in strain could become substantial.

One example of the potential effect of such a transient elevation instrain is explained with reference to FIGS. 15A-D.

Referring to FIG. 15A, a system having some or all of the featuresdescribed above may be arranged and set up to apply a relaxed lengthL_(s) of elastic strip material 42 to a length L_(B) of flat, unruffledsubstrate material such as backsheet material 50. The system may bedesigned to cause the strip material 42 to be longitudinally strainedprior to application, as indicated by the arrows. In the strainedcondition as shown in FIG. 15B, strip material 42 is then applied andaffixed to backsheet material 50 along length L_(B).

Following such application, strip material 42 may be allowed to relax.Elastic strip material 42 will seek to return to its relaxed lengthL_(s), and the affixed backsheet material 50 will develop transverserugosities 22, along strip material 42 as depicted in FIG. 15C.Transverse rugosities 22 consist of gathered backsheet material affixedalong relaxed strip material 42. If, prior to application, stripmaterial 42 is under uniform and constant strain, the flat, unruffledlength L_(B) of backsheet material 50 will be approximately evenlydistributed along the relaxed length L_(s) of strip material 42,gathered in the rugosities 22. The rugosities 22 may appear generallyevenly distributed in either quantity or size, or a combination thereof.Assuming consistency in respective material dimensions and properties,each of regions “E”, “F” and “G” as depicted in FIG. 15C generally willhave approximately equal linear quantities of backsheet material 50gathered and bonded along strip material 42.

If, however, the strain in strip material 42 is varied as it is beingaffixed to the backsheet material, the unruffled length L_(B) ofbacksheet material 50 may not be evenly distributed along the relaxedlength of strip material 42 after affixation, and relaxation. Forexample, referring to FIG. 15D, if there was an elevation in the strainin strip material 42 in region “F” as it was applied to backsheetmaterial 50, region “F” may have a linear quantity of backsheet material50 bonded along strip material 42 per relaxed unit length of stripmaterial 42, that is greater than in either of adjacent regions “E” or“G”. As depicted in FIG. 15D, this may manifest itself in a greaternumber of rugosities 22 per relaxed unit length of strip material inregion “F” as compared to the adjacent regions “E” and “G”. Anotherpossible manifestation is that the rugosities 22 in region “F” may begreater in size than those in the adjacent regions.

In some circumstances involving such variation in strain, the linearquantity of backsheet material gathered along strip material in a firstregion, per relaxed unit length of strip material, may be, for example,approximately 125 percent, approximately 150 percent, approximately 175percent, approximately 200 percent, or even more, than that in one ormore adjacent regions. This may evidence that the strain of the elasticstrip material as it was applied to the substrate material with thesubstrate material in flat, unruffled condition, was greater in thefirst region than in the one or more adjacent regions, by roughlycorresponding percentages. In a product such as a finished wearablearticle wherein the strip material encircles a leg opening, this maymanifest itself in a discontinuity or variation in the gathering ofmaterial about a leg opening.

Referring again to FIGS. 12-14, it is possible that substantialvariations of strain in the strip material 42 in zone “B” may in somecircumstances be deemed undesirable and unacceptable. In the exampledescribed immediately above, variations of strain in the strip materialas it is affixed to the backsheet material may result in leg openingswith discontinuity or variation in the gathering of material thereabout.In some circumstances this might be deemed to unacceptably compromiseproduct quality, appearance, fit or comfort. In other applications,specifications may call for relatively small variance in strain, if notsubstantially constant strain, of strip material. Thus, it may bedesirable in some circumstances to compensate for abrupt variations instrip path length in order to continuously regulate amount of strain inthe strip material 42 in zone “B”, before and as it enters joiningmechanism 200.

Such compensation may be provided by use of a feed servo motor 350driving one or both of feed rollers 301, 302. In one example, one offeed rollers 301, 302 may be driven by a feed servo motor, and the otherof feed rollers 301, 302 may be a passive, idling roller. Referring toFIGS. 12 and 13, the programming of servo motor 150 will be designed tocause the system to locate and apply the strip material 42 to thebacksheet material 50 along the profile required by the article design.Thus, the programming will contain information concerning the timing andmagnitude of angle θ by which the strip guide arm 100 is pivoted backand forth on a cyclic basis. This information can be used to programcyclic adjustments to the rotational speed of feed rollers 301, 302 (andthus, V₁) to avoid unacceptable variance of the strain of the stripmaterial 42 in zone “B”. Generally, in the example depicted, a rate ofincrease or decrease in the path length in zone “B” has the same effectas would an increase or decrease in the linear strip draw speed throughthe nip between rollers 201, 202. To avoid unwanted variations instrain, this increase or decrease may be offset by an equivalentincrease or decrease of the linear strip feed speed through the nipbetween feed rollers 301, 302.

For example, while angle θ is increasing, the strip path length isgrowing and V₁ may be temporarily increased in accordance with the rateof increase in the path length, which can mitigate or avoid anunacceptable elevation in strain of strip material 42 in zone B.

At any time period in which angle θ may dwell at a relatively constantvalue (as may be required by a particular article design), the strippath length also becomes constant, i.e., the rate of increase ordecrease in the path length in zone “B” becomes zero. In this event thesystem would cause strain in the strip material to approach the straindetermined by the initial values of V₁ and V₂, and V₁ may be returned toits pre-adjustment initial value to maintain substantially constantstrain of the required design (initial) value.

If after a dwell and substantial stabilization, angle θ decreases from apeak value abruptly enough to cause an unacceptable dip in strain belowinitial design value, a compensating adjustment may be made. Thus, whileangle θ decreases from a peak, V₁ may be temporarily decreased inaccordance with the rate of decrease in the path length, which canmitigate or avoid an unacceptable dip in the strain of strip material 42in zone B.

The requirement for such correction, and the programming of the feedservo motor 350 driving feed rollers 301, 302 to regulate strain in themanner described above, will be directed by factors including the designfeatures and specifications of the particular product beingmanufactured, the speed of the joining mechanism 200 and/or rollers 201,202, the programming of servo motor 150, the distance between the feednip and the upstream strip entry point 113, the length of the stripguide arm 100, and the distance between the distal end of strip guide102 and joining nip line 206.

A strain regulation/adjustment mechanism such as the example describedabove may be used for purposes other than maintenance of consistentstrain. There may be circumstances in which it is desirable tointentionally vary strain. For example, referring to FIG. 3, it can beseen that portions of strip material 42 affixed to partially completedportion 51 may be wasted because they occupy areas of completed portion51 that are to be cut away from the portion that forms outer chassis 28(FIG. 2). In order to minimize waste and conserve strip material, strainof strip material 42 in these waste areas may be increased, therebyreducing the quantity of strip material that is affixed in the wasteareas. A strain regulation/adjustment mechanism such as the exampledescribed above may be programmed to increase strain in the stripmaterial as it enters the nip between joining roller pair 201, 202 inlocations in such waste areas, and then return the strain to productdesign strain as the strip material enters the nip to be affixed innon-waste areas.

Every document cited herein, including any cross-referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A strip guide for laterally shifting a longitudinally moving stripmaterial as it enters a joining mechanism that urges the strip materialinto contact with a moving sheet material, the strip guide comprising asurface over which the strip material passes longitudinally, the surfacedefining a U-shape.
 2. The strip guide of claim 1 wherein the U-shapehas a curving portion that substantially comprises a semicircle having aradius.
 3. The strip guide of claim 2 wherein the strip material has astrip width, and the radius of the semicircle is approximately 21 toapproximately 43 percent of the strip width.
 4. The strip guide of claim3 wherein the U-shape has at least one substantially straight sideportion adjoining the semicircle, the side portion having a length, thelength being approximately 21 to approximately 61 percent of the stripwidth.
 5. The strip guide of claim 4 wherein the U-shape has twosubstantially straight side portions adjoining the semicircle, the sideportions having a length, the length being approximately 21 toapproximately 61 percent of the strip width.
 6. The strip guide of claim1 wherein the U-shape comprises an intermediate portion and two sideportions each adjoining the intermediate portion, and each respectiveside portion terminates at a respective strip edge guide.
 7. The stripguide of claim 1 wherein the U-shape comprises an intermediate portionand two side portions each adjoining the intermediate portion, and eachrespective side portion terminates at a respective strip edge stop.